This invention relates generally to underground fuel storage systems and particularly to a flow control valve assembly for the fill tube of an underground fuel storage tank.
In refilling underground fuel storage tanks such as the type commonly employed in gasoline filling stations, the supply hose from a tanker truck is coupled to the fill pipe of the underground storage tank and the fuel is gravity fed into the tank. In such systems, the fuel continues to flow unabated from the tanker truck until the tanker truck is empty, the operator closes the discharge valve on the tanker truck or until the storage tank is completely full thereby stopping any further flow. Since there is generally no means for alerting the operator that the storage tank is approaching a filled condition, the storage tank would be filled to capacity if the tanker truck initially contains more fuel than the unfilled capacity of the storage tank to be filled. Consequently, the discharge hose of the tanker truck is also filled with fuel which then presents a disposal problem. Typically, a filled supply hose may hold 25 gallons of fuel. Also, unless all of the pipe fittings are fuel-tight, the pressure exerted by the added head of fuel will cause these fittings to leak causing potential soil contamination.
Accordingly, it is an object of the present invention to provide a passive flow control valve which progressively reduces the flow of fuel into the tank as the quantity of fuel in the tank approaches a predetermined level in order to alert the tanker truck driver to the possible imminent overfilling of the storage tank and to allow the driver sufficient time to stop the flow of fuel.
Another object of the invention is to provide such a control valve which allows a small rate of flow when the valve is in the fully closed position so that any fuel contained in the supply hose may be drained into the storage tank.
Another object of the invention is to provide a passive flow control valve which can be retrofitted to existing fuel storage systems with minimum expense, labor, and structural modifications to existing fuel storage systems.
A further object of the invention is to provide such a passive flow control valve which is reliable in use, durable in construction, and economical to manufacture.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.